Xspice isn't very useful without the TCP connection possibility. When the port is busy:
$ Xspice --disable-ticketing --xsession /usr/bin/gnome-terminal :0 --port 5900
...
(/usr/bin/Xspice:6677): Spice-Warning **: reds.c:3037:reds_init_socket: reds_init_socket: binding socket to :5900 failed
...
If the port was explicitly requested, failure to bind should be prominently displayed, and preferably result in a termination of Xspice.
xorg-x11-server-Xspice-0.1.1-0.8.20130514git77a1594.fc19.x86_64